HEARTLESS vandals who graffitied a memorial bench for a six-year-old child who died of a rare brain tumour have been slammed by the boy's devastated family.

Cooper Christensen would have celebrated his ninth birthday on Sunday.

His family, including mum Amanda, dad Michael and his sister, Jessie Mahoney, visited the boardwalk at Torquay that was constructed in his honour in the months after he died.

The family were left shocked and disgusted when they visited the memorial park bench on Cooper's birthday on Sunday to find vandals had scratched words into the wood of the bench and had used markers to scrawl graffiti just centimetres from the plaque dedicated to their son.

Graffiti on the memorial bench for six-year-old Cooper Christensen, who died of a brain tumour in 2015.Contributed

Jessie said seeing the graffiti right next to plaque in Cooper's memory hurt the family deeply.

"I think that's what hurt mum the most," she said.

The family visit the boardwalk regularly, not only because of the memorial but because the Esplanade at Torquay was one of Cooper's favourite places.

Last month, the Christensen family held its second Cooper's Walk event on the Esplanade, to raise funds in the battle against brain cancer.

More than 100 people attended the event and released balloons into the sky.

Both Jessie and Amanda have visited the memorial in the days since then too, with both often stopping in to remember Cooper.

It would have been heartbreaking any day, but to see it on Cooper's birthday caused extra pain.